Actually, a living Warden romancing her gets more dialogue than a dead one. The gushy conversation where she gives you the operation to find the Warden obviously doesn't happen with a dead Warden, nor does the mention of them at Valence.
Whether a dead Warden fits more...that's a matter of debate. The letter from my Warden begging my Inquisitor to keep Leliana in the light was one of my feelsiest moments in the game, and added a whole new layer to that whole choice of softening her. I also just liked the feeling I got with my Warden and her, that she was basically the one last light in Leliana's life, but she's far, far away for who knows how long. The little glimmer of hope she gets after the letter was pretty 'd'aawww' worthy.
It was pretty endearing in general, how the Warden seemed to be the one thing that could lift her spirits.
A dead Warden fits better if you plan on a hardened Leliana, I suppose.
It'd also make her having no reservations about becoming Divine whatsoever a little less jarring.
Actually there is dialoiuge about a dead warden in valance. instead of ' i came here with the hof after the blight' its 'i needed 'something' after the hero of feralden died' and another dialouge about a dead warden, when u investigate an item there.
Thanks for the video, again, mrcrazyman! I won't be seeing it either, so it's interesting to see the other side of things.
As for Warden Alistair...yeah, I've got two world states with him, one US and one where I had him to do the Dark Ritual. He's pretty angry either way; either the Warden overshadowed him and he's sick of constantly hearing about her and people asking what it was like traveling with them (and I imagine he feels a bit useless when he missed the opportunity to be king and let a good friend die for him), or he, as you say, claims they've joined the dark side, as it were 
Since we're discussing it, what does Morrigan have to say about the different Wardens? The only one I remember was US, in which she said the thing she regrets most is how they parted. Looks like the best thing that could happen to Zev is not getting caught up in all of this for a change 
Actually, if you do wicked eyes and wicked hearts before adament, get morrigan, and then finish adament she will ask if you saw the hof there. i forget the actual dialouge, but it does suggest that she is friends with them. i ha e a save near there and can reload it to find what she says exactly.